Archaeozygodiscus gen. nov. and other Triassic coccoliths.
Paul Bown, University College London
Pre-Jurassic calcareous nannofossils have been reported by at least 14
authors since 1961 in rocks ranging in age from Cambrian to Triassic.
Despite these reports most workers remained skeptical about the existenceof pre-Jurassic nannofossils, especially coccoliths, until recent papers
by Moshkovitz (1982) and Jafar (1983) described and illustrated abundantand convincing material from the Upper Triassic of the Northern CalcareousAlps. The aim of this note is to described the genus Archaeozygodiscus
and finally dispel any doubt that may remain over the presence of
calcareous nannofossils and more importantly coccoliths in the Triassic bymeans of detailed scanning electron micrographs illustrating coccolithmorphology and ultrastructure.
The samples studied were personally collected from 7 published fieldsections within the Northern Calcareous Alps of Austria ranging in age
from Ladinian to Rhaetian.
Additional material was provided by Dr M
Urlichs.
From these 7 sections only samples from Kendelbachgraben,
Weissloferbach and Fischerwiese yielded nannofossils, with coccoliths fromthe latter two: Weissloferbach and Fischerwiese
exposerocksofNorian-Rhaetian (Hauptdolomit facies) and Rhaetian (Halstatt facies) age
respectively.
At least two species of coccolith have been observed by both light andscanning electron microscopy.
Both forms are relatively common (1coccolith per 10 fields of view) in the two sections and always occur
associated with an abundant and enigmatic assemblage of calcispheres andConusphaera zlambachensis Moshkovitz.
Taxonomy:
GENUS Archaeozygodiscus gen. nov.
Type species: Archaeozygodiscus koesseni sp. nov.
Diagnosis: Elliptical coccoliths possessing a loxolith structured rimimbricating
in an anticlockwise direction with an inner cycle oftangential and overlapping calcite laths.
Known Range: Norian-Rhaetian
Archaeozygodiscus koesseni sp. nov.
Plate 1, figs. 1-3.
Diagnosis: A species of Archaeozygodiscus with the short axis of theellipse spanned by a bar constructed from a number of calcite elements.
The centre of the bar has a circular hole which may or may not be a spinebase.

32

INA Newsletter vol. 7 - 1985

Remarks/Differentiation:
Superficially similar to the younger form
Zygodiscus erectus (Deflandre) Lezaud
but a number of features arethought to warrant the recognition of a new genus and species.
The
elliptical rim of A. koesseni possesses a typical loxolith structure as do
the coccoliths of zygodiscus, however, the elements are imbricating in theopposite direction and the rim includes an additional inner cycle oftangentialelements.
Archaeozygodiscus is also distinctive in its
diminutive size of 1.9 to 3.2 microns.
Holotype: Neg. no. UCL- 2040-33; plate l, fig. 1.
Paratypes: Neg. no. UCL- 2040-29; plate l, fig. 2.
Neg. no. UCL- 2028-10; plate l, fig, 3.
Dimensions: Length holotype 1.9 microns, width 1.4 microns.
Type locality: Weissloferbach, near Kossen, Austria.
Type level: Kossener Schichten; Ch. marshi ammonite Zone, Rhaetian.
Range: Upper suessi Zone, Norian to marshi Zone, Rhaetian.
GENUS Crucirhabdus Prins, 1969 ex Rood, Hay and Barnard, 1973.
Crucirhabdus minutus Jafar 1983
Plate l, figs. 4-7.
1983 Crucirhabdus minutus-Jafar, p.
lOb, 18.

247,fig.

12: 6a, 6b, 7, 8, 9, lOa,

First
describedbyJafar (1983) from light microscope
Remarks:
observations alone.
Further detailed examination by scanning electron
microscope reveals C. minutus to be a small coccolith approximately 2length possessing a highelliptical rim composed ofmicronsin
non-imbricating elements and a central area spanned by a cross which isorientated along the long and short axes of the ellipse.
The crosssupports a tall central spine.
Range: Upper suessi Zone, Norian to marshi Zone, Rhaetian.
References:Jafar, S A 1983 (INA code Al72-3)
Moshkovitz, S 1982 (INA code Al65-4)
Urlichs, M & Hagn, H (1981) Site C2: vJeissloferbach. Pages 135-141 inHagn, H. Die Bayerischen Alpen und ihr Vorland in MickropalaontologischerSicht. Geologica Bavarica 82: 1-408.
Acknowledgements:
This work is part of a project funded by the NaturalEnvironment Research Council and supervised by Dr A R Lord. I am greatlyindebted to Or Max Urlichs (Staatliches Museum fur Naturkunde Stuttgart)
for advice and sample material.

INA Newsletter vol. 7 - 198533

PLATE 1
1-3t Archaeozygodiscus ko1sseai gen. et sp. nov.
2040-33; distal vie~ 1 x 16,300; sample E136,
Fi9, 1: Holotype 1 UCL

Figs~

Fig~

2~

fig' 3:Paratype, UCL
2040-29; distal view, x 15 1 800; sample E136
Paratypa 1 UCL - 2036-25; proximal view, x 15,; sample E136,Figs. 4·-7: Crucirh~bdus 1iautus Jafar
F~ g, 4:
UCL - 2025-23; distal view, x 14,300; sample MCel39.
Fig . 5~ enlargement of cantral &rea af Fig. 4 1 K 22 1 000.
Fig.
Fig.

en7~UCL - 2040-13; distal view, x 15 1 000; sample El36.
UCL - 2025-9! distal view, x 16,500i sample W(e}39,Figs, 8,9: 'Crepi.dolithus' sp.
Fig. 8:UCL
2036-32; distal view, x 13 1 000; sample E136.

Fig, 9:UCL - 2036-33; distal view, x 15,000; sample E136.

All specimens above from 1arshi Zone, Rhaetian, Weissloferbach, Austria.
Specimen numbers refer to negatives stored in the Micropalaeontology Unit,
University College London.
Figs, 10a-10d: UFO 1,Fl.g.

lOa~Sph~nolithus

sp.

noma.rski:

Fig, lOb: oriented 60"' to x-nicols
Fig. 10c:~ oriented 10"' to x-r.icols
Fig. 10th oriented 27"" to x-nicols

Figs, U-13: UFO 2
magnification~ 2000 x34

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